Protecting electronic circuits from malfunctioning or becoming damaged by exposure to excessive current has long been a critical requirement. In practice, the reliable detection of the presence of over-current (OC) upon which circuit protection relies can be difficult due to some limitations. In power output stage circuitry, and gate drive circuitry in particular, the detection of over-current is complicated by the presence of noise, mainly due to ground bouncing and reverse recovery of power devices (either BJT or MOSFET). It is known in the arts to use various arrangements of analog circuit components to filter out the noise from an OC detection signal. Analog filtering solutions are beset with many problems, however, including variability due to power supply and process variations and imperfectly matched over-current detection circuit components. Usually, there is a wide distribution of OC limits if using analog filtering. As a result of these shortcomings, the over-current detection circuits known in the arts are subject to a tendency to erroneously report the existence of an over-current condition when such a condition does not in fact exist, causing unwanted interruptions and delays. Failure to detect over-current conditions as they occur, however, may permit excessive current to damage the device.
Due to these and other problems with over-current detection, there is a need in the art for over-current protection that is more accurate and less susceptible to noise.